The present invention relates to an arrangement on a packing machine to provide a product filling tube with a sterile filling atmosphere and to make possible a cleaning of the product filling pipe. The filling pipe belongs to a packing machine that is used primarily for the filling of packing containers with liquid foodstuffs.
In the packaging trade it is customary to pack contents of liquid foodstuffs, e.g. milk, in finished consumer packages of non-returnable character. Packaging of the foodstuffs most often is done with the help of modern, rationally operating packing machines which, at a high rate of production, manufacture filled, sealed packages under hygienically acceptable production conditions. The packing machines of the type referred to here operate to form, fill and seal packages from prefabricated, sheetlike blanks of a suitable packing material, usually plastic-coated paper which has been prepared with suitable decoration and with a pattern of so-called crease lines facilitating the fold formation. From flattened tubular package blanks, the machine produces packages wherein the packing blanks first are raised to form open, tubular packing boxes of generally rectangular cross-section with the aid of a so-called box-raising means. The box-raising means feeds the blanks one at a time from a magazine and deposits the raised blanks on a movable conveyor belt which conveys and transfers them to a first forming station of the machine where the one end or base of the boxes is closed. The base-forming station of the machine comprises an intermittently rotating mandrel wheel with radial mandrels. The radial mandrels are adapted to receive the boxes in the correct feed position on the conveyor belt for the stepwise transport of the same through a number of base-forming, shaping and sealing stations located around the mandrel wheel. The packing boxes provided with a base subsequently are removed from the mandrels and placed on a conveyor belt which is advanced synchronously with the indexing rotation of the mandrel wheel and which conveys the boxes provided with a base in upright position to the filling station of the machine where the boxes are filled with suitable portions of contents. The filling stations, which often are substantially surrounded by a covering machine casing, usually comprise a vertical product filling pipe opening into the filling station. Via product supply pipe with metering pump connected thereto, the filling pipe is joined to a tank containing the contents. The metering pump is adapted so as to pump from the product tank weighed portions of contents through the product filling pipe down into the packing boxes advanced centrally below the product filling pipe. From the filling station the filled packing boxes are conveyed to the final forming station of the machine where the boxes, by means of forming and sealing operations, are given a liquid-tight top closure. Thereafter, the boxes, the form of finished consumer packages, are discharged from the machine for further distribution.
As mentioned earlier, it is important that the packaging, especially in the case of contents of the foodstuffs type, takes place under guaranteed hygienically acceptable conditions. Among other things, this means that machine parts which come into direct contact with the contents should be protected as fully as possible, so as not to come into contact with the non-sterile environmental atmosphere of the machine. A certain protection against the environment is achieved with the help of the machine casing surrounding the filling station. Within the casing, a pressurized atmosphere of hot sterile air is maintained and non-sterile environmental air is effectively prevented from penetrating. The use of hot sterile air in the known packing machine has been found to entail certain inconveniences which, whilst possibly not representing any direct serious threat to machine hygiene, does in certain cases, involve the obvious danger of the hot air condensing on the outside of the filling pipe and dropping down into the packing boxes. The use of hot air of course also demands energy and thus increases cost. A hygienically unobjectionable packaging of foodstuffs moreover demands that at least those parts of the machine with which the foodstuffs come into contact are subjected regularly, usually in conjunction with normal operational stoppages at night, to an accurate cleaning or washing process. Such cleaning and washing is necessary so as to remove and prevent the risk of foodstuff deposits promoting bacteria growth which, especially when using hot sterile air, seriously jeopardize the prerequisites for the machine complying with the threshold standards of hygiene. Such a machine component requiring special care and attention is of course the product filling pipe of the machine. It has been necessary up to now first to dismantle and remove this part from the machine in order successfully to clean it on its outside as well as its inside, and afterwards to reinstall it in the machine. Apart from this cleaning operation being time-consuming and requiring manual functions for the disassembling and reassembling of the filling pipe, it is unsatisfactory also in that the machine operator risks coming into contact with, and polluting, the outside of the product filling pipe during reinstallation.